Larry Strain, FAIA, LEED AP is a co-lead of EcoBlock’s Design/Construction team and Principal at Siegel & Strain Architects, an award-winning architecture and planning firm in the East Bay. An advocate for reusing and retrofitting existing buildings, Larry has conducted industry-leading research on embodied carbon, which has helped establish methods and benchmarks for designing lower-impact buildings. This month, we sat down with Larry to discuss his work on embodied carbon and the growing importance of adaptive reuse in the built environment.
This interview has been edited for length and clarity.
EC: What is embodied carbon, and why is it important?
LS: Embodied carbon is all the carbon (CO2) that goes into making a building. It’s the carbon that’s released during the extraction, manufacturing, and transportation of materials and the construction processes used over the long lifespan of a building. This is different from operating carbon, which is the carbon that’s created by the gas and electricity used to heat and power a building.
Embodied carbon relates so well to reuse because the more buildings you reuse, the fewer new buildings you have to build. You have a minor investment in the remodel and save a lot of the carbon emissions compared to building a new building.
How does this relate to the EcoBlock project?
It’s about maximizing the total carbon emissions. The embodied carbon savings for one single-family home aren’t huge, but when you have a whole block of homes, it adds up. Embodied carbon is also important because in a new home, embodied carbon emissions occur at the beginning of the building’s life and are equal to something like ten years’ worth of operating emissions, so over the next ten to twenty critical years, embodied carbon is usually more than the operating carbon for a new home.
But EcoBlock isn’t just about embodied carbon. It’s about the total carbon that’s saved and avoided compared to building new, energy-efficient, and net-zero energy homes. It’s equally important that we’re doing the energy upgrades, microgrid, and net-zero retrofits—all that plays into it. In fact, the operating carbon is going to save you more over time. We have to think of it as operational savings and embodied savings altogether.
How can one maximize the amount of embodied carbon that’s saved for existing, retrofitted buildings, like those for EcoBlock?
It’s mostly about reusing the carbon-intensive parts of a building, like the concrete foundation. It’s also about selecting low-carbon materials for the renovation and upgrade. For example, avoid foam insulations with a high global warming potential (GWP). Insulation, such as blown-in cellulose, has a very low carbon footprint—and because it’s made from recycled newspaper, it can be considered a carbon-storing material.
So embodied carbon is a part of the bigger picture.
Yes, and let me show you a tool we are developing to help see the whole picture. This is the 2Build or not 2Build Carbon Calculator, which compares the total carbon impacts of renovating an existing building versus building a new one.
The chart on the left is the run I did for a typical EcoBlock home. It shows the embodied, operating, and avoided carbon impacts of the home under three circumstances: when it’s (1) left alone, (2) retrofitted, and (3) completely torn down and replaced with a new home.
The chart on the right shows the total carbon emissions of the home over time for those three cases. The red line shows that if you left your building alone for twenty years, you would emit 54 tons of carbon in total; the green line shows the investments needed to make a net-zero remodel; and the blue line shows the investments needed to build a brand new, net-zero building.
You can see that the red and green lines intersect at the two-year mark—meaning that after two years, you’ve offset all the carbon that was produced from retrofitting the building. From then on, there aren’t any carbon emissions. Whereas if you built a new, net-zero building—that’s where the red and blue lines intersect—it would take you ten years to achieve the same effect.
Not only is embodied carbon part of the story, but for the first few years of a building’s life, it’s the most important type of carbon there is. The operating carbon grows steadily every year, adding more carbon emissions simply because you’re operating the building. But there’s this initial investment of carbon to make a remodel or a new building—and if it’s net zero, there aren’t any more emissions to be made. This initial investment of almost 30 tons of carbon to build a new single-family home goes down to six tons to do a remodel.
Does the type of building that’s remodeled affect how much carbon is saved? That is, whether it’s single-family homes, multifamily apartments, duplexes, etc.
Single-family homes probably have the lowest carbon savings because it doesn’t take a lot of embodied carbon to build a home. Other than the concrete foundation, a house is mostly built with wood, which isn’t a very carbon-intensive material. Reusing large commercial buildings is even more effective because this building type uses carbon-intensive materials like steel and concrete.
Remodeling a home makes sense because you usually preserve your concrete foundation, which makes up about 50 percent of your carbon emissions. When you’re remodeling, not only are you saving materials, but you’re working with the low-carbon pieces of a building—whether that’s the interior walls and maybe some windows—and avoiding the foundation altogether.
How do you see the Carbon Calculator evolving? Would there be different versions based on building type?
Yes, I think we may end up with multiple tools. I’ve never really used the calculator for single-family homes because it was originally designed for commercial buildings.
When I used the calculator to explore a typical EcoBlock home, I realized that we might need a different model that had slightly different inputs for residential buildings because the numbers are based on emissions per square foot. The emissions are different for a single-family home than they are for a commercial building. Ideally, you’d have a residential building calculator and a commercial building calculator—the base model would stay the same, but the inputs would differ.
It’s interesting because the numbers aren’t that huge at an individual house scale. It’s when you add them all up at the block scale that the numbers become larger, similar to that of big commercial buildings. If we’re trying to look at the total carbon offsets that the entire EcoBlock offers us, the embodied carbon would become an important part of the story.
So the carbon savings of multiple single-family homes are comparable to that of one or two commercial buildings.
That’s right. All the inputs are based on the square footage for your building type, not your specific building. If you add all the homes together, you can treat them as one big building, which makes it easier to understand the big-picture impact.
The light blue bar on the left shows the carbon savings of a retrofitted single-family home compared to that of a new one. You’re saving 22 tons of carbon in this one building versus building a new building. If you did that across the whole EcoBlock, you would be saving hundreds of tons of carbon.
How has your research on embodied carbon shaped your work as an architect? In general, the public perception of architecture—as well as what’s taught in most architecture schools—aligns the discipline with the design of new buildings rather than existing ones.
That’s a good question. I came out of the same tradition that new buildings were where it’s at and the more design freedom you had, the better.
It was this aha moment I had about seven or eight years ago. It’s like, why are we spending all this time trying to invent new materials when the materials are already embedded in our existing buildings? Let’s just use them. So that’s how it changed my thinking.
We still build new buildings at Siegel & Strain but look for opportunities to remodel whenever we can. We typically build in wood and really low-carbon concrete and don’t do steel or steel frame buildings—partly because we don’t work at that scale and partly because we don’t believe in them. This is something we’ve been doing for a long time.
Remodeling existing buildings seems a lot more feasible than building new ones.
We’ve done a few projects that took an existing but not-so-nice building and turned it into something beautiful. Not only are you making the building more efficient, but you’re also making it more beautiful and functional, which is harder to do than starting from scratch. I really honor the architects who transform existing buildings, both aesthetically and functionally, while reusing all those incredible materials.
There’s a wonderful building in Portland, OR—the Edith Green-Wendell Wyatt Federal Building—that removed the concrete exterior panels of an existing, 1970s office building and encased it in this incredibly beautiful sunscreen.
The renovated building won all these awards and uses significantly less energy. Even though the architects used pretty high-carbon materials—like aluminum in the sunscreen—the building was so much lighter that it eliminated the need to do a structural upgrade.
It’s truly a stunning building. If we put all that design energy into reimagining what we already have, we’d have something.
Last but not least, why architecture?
Well, I was a carpenter for ten years before I went back to architecture school. I built houses and did remodels for a while. I also studied environmental systems at Evergreen State College and then at the Farallones Institute working on solar staff cabins and passive design. So I came into architecture from a building and environmental standpoint.
The whole community and social aspects of architecture are also important to me, and I think reusing buildings and caring for existing communities support those facets of design. I also like the physical aspect of building a lot—I’m the person in our office who often reviews construction details or figures out how things go together because I enjoy that.
Architecture is a holistic practice, but it hasn’t been holistic from an environmental standpoint—we’re getting there. It’s still hard to sell architects on remodeling buildings; everyone wants to design a new building.
It’s a work in progress.
I think so. It would be good if we can get people to start giving awards for really brilliant remodels and renovations and have those on the cover of magazines instead of just the big new buildings. That’s partly what kids in school pay attention to. If remodeling becomes the hot new thing, then maybe we’ve got a chance. It can’t just be a technical or energy solution, it’s got to be about great design too. We have to figure out how to do both.
Cover image: The Edith Green-Wendell Wyatt Federal Building before and after its transformation. Credit: James Cutler & SERA Architects